A small subpopulation within NINCDS Collaborative Perinatal Project children has been identified as being of mixed black and white parentage. Within the interracial group of matings there is no evidence that genetic or socio-economic differences are related to race of mother (or father). Thus socio-psychological influences, presumably operating through mother-child interactions, can be examined indirectly. Two papers have been published which indicate that, although early childhood differences are wholly negligible, children of white mothers eventually develop positive intellectual differentials. A careful reanalysis suggested by a journal referee of the comparative rates of growth of interracial and control children has removed the appearance of important dfferences. It is probable that no revised manuscript will be prepared.